A fuel cell has been known, whose cell characteristics including a cell voltage are enhanced by preventing the stay of water in an electrode layer, particularly the stay of water in and around an interface between a gas diffusion layer and a catalyst layer (see Japanese Patent Application Publication No. 2001-338651, for example).
The cell voltage of the fuel cell is enhanced by setting the pore diameters of pores in the catalyst layer and the gas diffusion layer in each of the anode and cathode in a way that a pore diameter distribution has a peak in a range not greater than 0.1 μm, preferably in a range of 0.03 μm to 0.05 μm.
However, the fuel cell has a problem that the fuel cell is not sufficiently reliable due to a long-term characteristic in which the cell voltage decreases to a large extent over time, although the fuel cell provides a high cell voltage as an initial characteristic.
In addition, Japanese Patent Application Publication No. 2001-338651 states that it is desirable that in the pore diameter distribution, a peak area in a range not greater than 0.1 μm should occupy not less than 5% of a total peak area in order to obtain a practical effect of the aforementioned setting, but includes neither any description nor suggestion concerning a relationship between the pore diameter distribution and the time dependency of the cell voltage.